Diabatic-basis potential-energy curves for electronic states of N₂ relevant to interstellar photodissociation. Blue curves: states. Black curves: states. Red curves: states. Green curve: state. The energy scale is referenced to the v = 0,J = 0 level of the ground state (not shown). The lowest dissociation limit, N(⁴S) +N(⁴S) at ~78 715 cm^-1 (9.76 ev), is beyond the scale of the figure. The H ionization potential of 13.6 eV provides an upper limit to the interstellar radiation field and corresponds to 109 691 cm^-1.